How will you convert the following ?
Bromoethane to iodoethane.

Bromoethane can be converted to iodoethane by Finkelstein reaction.

Bromoethane reacts with in presence of $NaI$ in presence of acetone and gives iodoethane with $NaBr$.

$\underset{\text{Bromoethane}}{C_2{H}_5-Br}+NaI\stackrel{\text{acetone}}{\to }\underset{\text{Iodoethane}}{C_2{H}_5-I}+NaBr$